Frequency converter



FIG. 1 is a rear view of a frequency converter comprising a new, original and ornamental design;

FIG. 2 is a bottom view thereof;

FIG. 3 is a front view thereof;

FIG. 4 is a front, left side and top perspective view thereof;

FIG. 5 is a left side view thereof;

FIG. 6 is a right side view thereof;

FIG. 7 is a top view thereof;

FIG. 8 is a rear view of a frequency converter in accordance with another embodiment;

FIG. 9 is a bottom view thereof;

FIG. 10 is a front view thereof;

FIG. 11 is a front, left side and top perspective view thereof;

FIG. 12 is a left side view thereof;

FIG. 13 is a right side view thereof; and,

FIG. 14 is a top view thereof. 

CLAIM The ornamental design for a frequency converter, substantially as shown and described. 